Mars suit

A Mars suit or Mars space suit is a space suit for EVAs on the planet Mars. Compared to a suit designed for space-walking in the near vacuum of low Earth orbit, Mars suits have a greater focus on actual walking and a need for abrasion resistance. Mars' surface gravity is 37.8% of Earth's, approximately 2.3 times that of the Moon, so weight is a significant concern, but there are fewer thermal demands compared to open space. At the surface the suits would contend with the atmosphere of Mars, which has a pressure of about 0.6 to 1 kilopascal (0.087 to 0.145 psi). On the surface, radiation exposure is a concern, especially solar flare events, which can dramatically increase the amount of radiation over a short time. Some of the issues a Mars suit for surface operations would face include having enough oxygen for the person as the air is mostly carbon dioxide; in addition the air is also at a much lower pressure than Earth's atmosphere at sea level. Other issues include the Martian dust, low temperatures, and radiation.

Overview

One design for a Mars suit from the 2010s, the NASA Z-2 suit, would have electroluminescent patches to help crew members identify one another. Three types of tests planned for the Z-2 include tests in a vacuum chamber, tests in NASA's Neutral Buoyancy Laboratory (a large pool for mimicking zero-g), and tests in a rocky desert area. (See also: Z series space suits.) The Mars 2020 Perseverance rover has a materials test that is hoped will aid Mars suit development, the SHERLOC experiment; it includes a test target with space suit materials. The test will measure how these suit materials are affected by the Martian environment. Six materials have been chosen for testing: Orthofabric, Teflon, nGimat-coated Teflon, Dacron, Vectran, and Polycarbonate. The test will help select the best materials for future Mars space suits. Orthofabric is a polymeric material composed of a weave of GORE-TEX fibers, Nomex, and Kevlar-29. NASA tested possible Mars space suit materials by exposing them to Mars-equivalent ultraviolet (UV) radiation for 2500 hours, and then studied how the materials were affected. One of the concerns for the Mars suits is how materials respond to chemically reactive Mars dust and exposure to ultraviolet, especially over the lengths of time and amount of use the suits are expected to function. One researcher working on a design for Mars surface EVA suits was inspired in part by Medieval armor suits. Some ideas for a Mars suits are a Heads-up display projected in the visor, built-in communications equipment, life support, and a voice-recognition assistant. Examples of design concerns:

High-speed winds filled with abrasive Mars dust Radiation such as cosmic rays Low temperatures down to −130 °C (−202 °F; 143 K) Exposure to ultraviolet light One Mars mission design aspect is whether the Mars suits should also be made to work in space, or should be for the surface only.

Designs

The Biosuit is a mechanical counterpressure suit, resulting in a body hugging form. In this type of suit, the pressure would come from the structure and elasticity of the material, whereas with prior space-worn suits the pressure comes from pressurized gas, like a filled balloon. The gas pressure can make a flexible suit very rigid, like an inflated balloon. The Aoudo suit by the Austrian Space Forum is a space suit simulator for planetary surfaces. The suit ventilates with ambient air, but has a host of features to help simulate a space suit as well as tests enhancing technologies like a heads-up display inside the helmet. The AX-5 was part of a line of hard-suits developed at NASA Ames. Current suits are either soft or hybrid suits and use a lower-pressure pure oxygen atmosphere, which means people going on EVA must pre-breathe oxygen to avoid getting decompression sickness. A hard-suit can use a high-pressure atmosphere, eliminating the need to pre-breathe, but without being too hard to move like a high pressure soft suit would be. A simulated Mars suit was used for the HI-SEAS Earth-based spaceflight analog tests of the 2010s in Hawaii, USA. Mars suit design has been used as a topic for technology education.

Comparison to Apollo lunar suit

The Apollo lunar EVA suit was called the Extravehicular Mobility Unit (EMU). Besides the pressure suit, this included the Portable Life Support System (backpack) and an emergency Oxygen Purge System (OPS) which provided 30 minutes of oxygen for emergency. The combined system weighed 96.2 kilograms (212 lb) on Earth, but only 15.9 kilograms (35.1 lb) on the Moon.

Environmental design requirements The most critical factors for immediate survivability and comfort on the Martian surface are to provide: sufficient pressure to prevent the boiling of body fluids; supply of oxygen and removal of carbon dioxide and water vapor for breathing; temperature control; and protection from cosmic radiation.

Pressure

The atmospheric pressure on Mars varies with elevation and seasons, but there is not enough pressure to sustain life without a pressure suit. The lowest pressure the human body can tolerate, known as the Armstrong limit, is the pressure at which water boils (vaporizes) at the temperature of a human body, which is about 6.3 kilopascals (0.91 psi). The average surface pressure on Mars has been measured to be only about one-tenth of this, 0.61 kilopascals (0.088 psi). The highest pressure, at the lowest surface elevation, the bottom of Hellas Basin, is 1.24 kilopascals (0.180 psi), about twice the average. There is a seasonal variation over the Martian year (about two Earth years) as carbon dioxide (95.9% of the atmosphere) is sequentially frozen out, then sublimated back into the atmosphere when it is warmer, causing a global 0.2-kilopascal (0.029 psi) rise and fall in pressure. But the Martian atmosphere contains only 0.13–0.14% oxygen, compared to 20.9% of Earth's atmosphere. Thus breathing the Martian atmosphere is impossible for almost any organism; oxygen must be supplied, at a pressure in excess of the Armstrong limit.

Breathing

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